1. Field of the Invention
This invention relates generally to a vibration-damping device for miniature motor brushgear, and more particularly to a vibration-damping device for miniature motor brushgear in which the unwanted vibration of brushes caused by the rotation of the commutator is prevented by applying a soft photo-setting resin on the brush arms.
2. Description of the Prior Art
In recent years, an increasing number of miniature motors are being widely used as drive motors for audio equipment, industrial equipment and office equipment.
FIG. 3 (A) is a partially cut-away side elevation of such a miniature motor.
FIG. 3 (B) is a diagram of assistance in explaining the state where brushes are supported by a motor case cover.
In FIGS. 3 (A) and (B), reference numeral 1 refers to a brush arm; 2 to a brush base; 3 to a terminal; 4 to a motor case; 5 to a motor case cover; 6 to a bearing; 7 to a brush insertion hole; 8 to a rotor; 9 to a commutator; 10 to a magnet; 11 to a shaft; and 12 to a shaft hole, respectively.
As shown in FIG. 3 (A), the shaft 11 to which the rotor 8 and the commutator 9 are fixedly fitted is rotatably supported by the bearings 6 provided on the motor case 4 and motor case cover 5 in motor case 4 incorporating magnet 10. The brush arms 1 making contact with the commutator 9 are fixedly fitted to the motor case cover 5 as the brush bases 2 are inserted into the brush insertion holes 7 provided on the motor case cover 5, as shown in FIG. 3 (B).
The brush arm 1 fixedly fitted to the motor case cover 5 in the abovementioned state tends to cause unwanted chattering and to deteriorate commutating performance due to the vibration resulting from the irregular surface of the commutator 9 as the brush arm 1 slides on the commutator 9. Conventional means to prevent such an unwanted phenomenon include a brush vibration-damping device comprising a rubber sheet or film applied onto the brush arm 1 with a rubber or acrylic adhesive.
FIG. 4 (A) is a front view of a conventional brush vibration-damping device consisting of a rubber sheet applied onto the brush arm. FIG. 4 (B) is a side elevation of the same.
In the figures, numeral 13 refers to a rubber sheet; 14 to a fork-like prong of the brush arm 1.
When the vibration-damping rubber sheet 13 is applied on the brush arm 1 as a vibration damper, the rubber sheet 13 and the fork-like prongs 14 are formed into an integral part, and as a result the independent resiliency of each prong 14 is lost. This leads to deteriorated sliding contact between the fork-like brush arm 1 and the commutator 9 and the loss of the spark-quenching effect brought about by the multi-point contact with the commutator of the brush arm fork-like prongs. Furthermore, this arrangement involves an additional operation of applying a cut length of the rubber sheet 13 on the brush arm 1.